Automatic switch



Nov. 11 1924' M. SKENDER AUTOMATIC SWITCH Filed Sept. '7. 1923 3Sheets-Sheet. l

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Nov. 11 1924- M. SKENDER AUTOMATIC SWITCH Filed Sept. '7. 1923 3Sheets-Sheet 2 Wt'nesses:

Nov. 11 1924.

M. SKENDER AUTOMATIC SWITCH Filed Sept. 7. 1923 3 Sheets-Sheet 3 17am):W. M07452 Jen/are,

Patented Nov. 11, 1924.

MICHAEL SKENDER, OF IPITTSBURGH, PENNSYLVANIA.

AUTOMATIC SWITCH.

Application filed September To all whom it may concern:

Be it known that I, MICHAEL SKENDER, a citizen of the United States, andresident of East End, Pittsburgh, in the county of Allegheny and Stateof Pennsylvania, have invented" certain new and useful Improvements in"Automatic Switches, of which the following is a specification.

This invention relates to switches, and more particularly to automaticlimit and reversing switches, and has for one of its objects therovision .of a switch of this class adapted to prevent the over-runningof hoistin cranes and the like.

Anot er object is to provide .a switch which will be normally held inposition to normally complete the field circuit to the motor in thedlrection of operation and will, when tipped automatically, break thiscircuit and make areverse field circuit.

A further object is to provide means for holding the switch in reverseposition after it has been tripped, until the controller is moved to offor neutral position.

A still further object is to provide a switch of the class describedhaving the novel construction, combination and desi of parts hereinafterdescribed and illustrated in the accompanying drawings.

In the drawings, Figure 1 is a top plan of a switch constructed inaccordance with my invention, the cover being removed for clearness.

Figure 2 is a front side elevation.

Figure 3 is an end elevation showing counterweight operating mechanism.

Figure 4 is an end elevation taken opposite Figure 3.

Figure 5' is a rear side elevation in combination with a wiring diagram.

Referring more particularly to the drawings, the letter A designates-thesupporting structure of the switch as a whole, which supports the switchparts and is composed of a ba'se2, end walls 3 and 3" and back wall 4.Preferably when in use a housing or cover (not shown) will be providedto enclose the supporting structure and working parts of the switch.

A pair of dividing wallsor artitions 5 and 6, secured to the base andback wall 2 and 4, respectively, serve to divide the s ace between theend, walls 3 and 3' into t ree separate working chambers.

Upper and lower contacts 7 and 8 are 7, 1923. Serial No. 661,462.

mounted on the back wall between the end wall 3 and dividing wall 5, andother upper and lower contacts 9 and 10 are mounted on the back wallbetween the dividing walls 5 and 6.

A shaft 11 is journaled in suitable bearings in the end walls 3 and 3,and the portion of the shaft extending from the dividing wall 6 to theend wall 3 is provided with an insulated sleeve covering 12.

A pair of contact arms 14 and 15, secured on the sleeve covered portionof the shaft 11, are connected by flexible connecting strips 14 and 15to binding posts 14 and 15*, respectively, and arranged to contact witheither the upper contacts 7 and 9 or lower contacts 8 and 10, accordingto the position of the shaft 11.

A solenoid core 16 is mounted in the space between the wall 6 and endwall 3" and isadapted to be energized when the shaft is rotatedclockwise so as to cause the arms 14 and 15 to contact with the contacts8 and 10, and a solenoid plunger 17 is secured on the shaft 11 so thatit will be attracted b the energized core 16 and hold the sha t inposition.

A lever arm 19 is secured intermediate its ends at 20 to the end of theshaft 11 which projects through the end wall 3 and a counterweight 21 isrigidly secured to one end of the lever while its other end has aslightly heavier counterweight 22 suspended therefrom by a cable 23. Thecounterweight 22 is provided with a cable arm 24 having an aperturetherein through which one of the hoisting cables of a crane is passed asdesignated by the numeral 25. The cable 25 is provided with a stop block26 adapted to engage the counterweight 22 and lift the same as the loadis lifted beyond its safe limit, or predetermined point.

In Figure 5 a diagram of the circuits made by the switch, whencontrolling a series wound motor, is shown. The numerals 27 and 28designate the positive and negative feed wires, respectively, 29designates the controller and 30 and 31 designate the motor field andarmature, respectively.

Assuming that a load is to be raised, the controller 29 is moved to theproper position which will cause a circuit to be made from the plus line27 through the binding post 14, connection 14 and arm 14 to contact 7,thence through wire 33 to the motor field 30, through the field 30,thence through troller 29, wire 37 to armature 31, through the armatureto wire 36, through controller 29 to wire 28 on other side of line.

When the load is raised to its upper limit, the stop block 26 willengage the cable arm 24 and raise counterweight 22, thus permitting thecounterweight 21 to rock the shaft 11 clockwise, breaking the contactbetween the arms 14 and 15 and the respective contacts 7 and 9 makingcontact immediately with the contacts 8 and 10, respectively, which willcause a reverse flow of current through the motor field 30 and therebycause the motor to rotate in the reverse direction and lower the load,which movement Will continue until the circuit is broken by the operatormoving the controller 30. i

I When the arms 14 and 15 have made contact with the contacts 8 and 10the following circuit will be made, from positive wire '27, post 14connection 14, arm 14, contact 8, to wire 40 to coil or solenoid core16, through core 16 to Wire 41, thence through a resistance 42, to wire43, wire 34, to the motor field 30, through the field 30 to wire 33 tocontact 7, thence through a connecting wire 44 to contact 10, thenthrough arm 15, connection 15, and post 15*, to w'ire35, throughcontroller 29 to wire 37 to armature 31, through the armature to wire36,through controller 29 to wire 28 on other side of line. It will bereadily understood that the above circuit will cause the reverseenergization of the field 30 and reverse rotation of the motor.

By including the resistance 42 in the reverse motor circuit theenergization of the motor will be weakened so that the reverse rotationof the motor caused by the operation of this switch will be slower thanwhen a direct circuit is made in the usual manner through thecontroller.

In operation, when the crane or other hoisting apparatus is raising aload, if the operator neglects to stop the motor before the stop block26 engages the counterweight 22, the switch will operate toautomatically break the forward or lifting circuit to the motor fieldand immediately make the reverse circuit above described, which willserve to stop the forward or hoisting movement of the motor and cause itto operate in the reverse direction to lower the load, although suchlowering will be considerably slower due to the resistance 42.

The downward movement of the load will attract the operators attention,and he will then move the controller to neutral position and break allcircuits through the controller, thus stopping the operation of themotor and de-energizin the solenoid coil 16. When the coil 16 1s(lo-energized the counterweight 22 will cause the shaft 11 to rotate ina counterclockwise direction, providing the load has moved downward asuflic-ient distance for the stop 26 to release the counterweight 22,thus causing the arms 14 and 15 to again engage the contacts 7 and '9.If the load has not been lowered a sufiicient distance for the stop torelease the counterweight 22, the switch arms 14 and 15 will remain incontact with the contacts 8 and 10, and it will be impossible for theoperator to raise the load by completing a forward circuit to the field30, since such circuit will be transposed into a reverse circuit by theswitch and cause the motor to rotate in a reverse direction soas tolower the load.

It will also be noted that once the/switch arms 14 and 15 have engagedthe contacts 8 and 10 to make a reverse circuit to the field 30,theywillremain in thisposition due to the action of the solenoid until thecircuit is broken by the controller 29, regardless of the position ofthe counterwei hts, thus preventing a continuous reversal of directionand the up and down movement of the load as would be caused if thecounterweights alone controlled the position of the switch arms.

I claim 1. A limit and reversing switch comprising a body portion, ashaft mounted forrotation in said body portion, counterweights forrotating said shaft, an insulated sleeve on said shaft, a plurality ofdouble acting contact jfingers secured on said shaft, rigid contacts onsaid body portion adapted to be engaged by said contact fingers, andmeans for holding said contact fingers in reversing position after saidswitch has acted to automatically make the reverse circuit until thecircuit through said switch is broken.

2. A limit and reversing switch comprising a body portion, a shaftmounted in said body portion, means for automatically operating saidshaft, a plurality of contact fingers on said shaft,'contact elements onsaid body portion adapted to be engaged by said contact fingers tocomplete the clrcuits through said switch, said shaft being adapted tobe automatically rotated to disengage said fingers from some of saidcontacts and engage said fingers with other of said contacts to breakthe forward circuit and make a reverse circuit, and means for holdingsaid fingers in reverse contact after said switch has acted to make thereverse circuit until the circuit through said switch is broken. r

3. A limit and reversing switch compris ing a body portion, a shaftmounted in said body portion, means for automatically operating saidshaft, a plurality of contact fingers on said shaft, contact elements onsaid body portion adapted to be engaged by said contact fingers tocomplete the circuits through said switch, said shaft being adapted tobe automatically rotated to disengage said fingers from some of saidcontacts and engage said fingers with other of said contacts to breakthe forward circuit and make a reverse circuit, a solenoid core armsecured to said shaft, and a solenoid coil adapted to be energized whenthe reverse circuit is made through said switch, said energized coilbeing adapted to attract and hold said core arm, thereby preventing therotation of said shaft.

4. The combination with a hoisting cable, a motor for furnishing thepower to operate said cable, and a controller for making and breakingthe circuit to said motor, of means independent of said controller andoperable automatically when said cable reaches a predetermined point inits hoisting travel for breaking the forward circuit to said motor andmaking a reversing circuit, said means being adapted to maintain saidreversing circuit until said controller is moved to off or neutralposition.

5. The combination with a hoisting cable, a motor for furnishing thepower to operate said cable, and a controller for making and breakingthe circuit to said motor, of a combined limit and reversing switchthrough which the circuit from said controller to said motor is made,said switch being normally in position to complete a forward or hoistingcircuit to said motor and being adapted to be automatically operated bysaid cable at a predetermined point in the hoisting travel of said cableto break said forward circuit and complete a reverse circuit to saidmotor, means normally tending to return said switch to position to makesaid forward circuit, and means for preventing said return operationuntil said controller has been moved to neutral or off position.

6. The combination with a hoisting cable. a motor for furnishing thepower to operate said cable, and a controller for making and breakingthe circuit to said motor, of a combined limit and reversing switchthrough which the circuit from said controller to said motor is made,said switch comprising a pair of double acting contactin fingers, aplurality of contacts for sai fingers, means for normally holding saidfingers in engagement with some of said contacts to close the forwardcircuit from said controller to said motor, meahs for automaticallytripping said fingers to disen age them from said contacts and engage tem with other of said contacts when said hoisting cable reaches apredetermined position, thereby breaking said forward circuit and makinga reverse circuit to said motor without operating said controller, andelectrically operated means energized by said reverse circuit adapted tohold said switch in reverse position regardless of the position of saidtripping means until said controllcr is moved to neutral or offposition.

7. The combination with a hoisting cable. of a motor control comprisinga motor having the usual armature and field, a source of electricenergy, a controller for making and breaking the usual circuits to saidmotor armature and field, and an automatic limit and reversing switchconnected in the motorfield circuit between said controller and saidfield, said switch being provided with a pair of double contact fingers,a pair of forward and a pair of reversing contacts for said fingers,means for normally holding said fingers in engagement with said forwardcontacts so as to complete a forward circuit from said controller tosaid field, means for automatically tripping said fingers to disengagesaid fingers from said forward contacts and engage them with saidreversing contacts, thereby breaking said forward circuit and making areverse circuit to said field, a solenoid core 'arm connected with saidfingers, a solenoid coil connected in the reverse field circuit andadapted to attract and hold said core arm, thereby preventing the returnof said fingers to their normal position until said controller is movedto off position to open the circuits through said switch.

In testimony whereof I have hereunto set my hand.

MICHAEL SKENDER.

